6 ms·

We had geothermal put in when we built new. Given a suburban MD lot and the large size of truck necessary to bore two 350' deep wells, it's far too messy a job

We had geothermal put in when we built new. Given a suburban MD lot and the large size of truck necessary to bore two 350' deep wells, it's far too messy a job to do without trashing the site due to all the water and resulting mud. It exchanges 55F year-round (closed loop with just water running through the tubing). It's been running quite reliably for 9 years now. We nearly tripled the square footage but our total energy costs stayed almost exactly the same. Went from gas heat/electric cooling to all electric geothermal. We still have natural gas for a backup generator, cooking and laundry dryer. We kept gas for kitchen/washing because there's a monthly minimum for gas service that we'd use for the generator. DC's Pepco power is notoriously unreliable.

ncmncm 4y ago
They quoted $50,000 to $90,000 for me. That would be quite some years' bills. Near-surface geothermal seems a better investment, if you have room for it.
- wkearney99 4y ago
  State and federal tax credits offset it somewhat. There's also the benefit of, y'know, not burning fuels at the site. My paying somewhat more over time for the initial outlay seems a reasonable expense. A purely selfish side-effect is NO NOISE from outdoor condenser fans. Three of them necessary would have wasted a lot of space too, and been more maintenance items. Near surface only works if you've got a lot of square footage to spread it out. The average suburban lot would not have the space for it (I thought that would have been obvious).
  - ncmncm 4y ago
    As I said, "if you have room for it".
benj111 4y ago
You're talking about a ground source heat pump though? Which is distinct from geothermal.
- ncmncm 4y ago
  The sales people all call it geothermal. We might need to retroname the old one... Geosteam? Borehole? Maybe a closed-cycle nitrogen or helium turbine would make for fewer overhauls, thus lower maintenance cost, vs. exposing your turbines to superheated steam all the live-long day.
  - dredmorbius 4y ago
    The two broadest classifications I see are Geothermal Power Generation and Geothermal Heating. These each have further subdivisions (and may be combined, as in a generation-heating facility, fairly common in Iceland). Generation can be divided in several ways. There are vapour and fluid-dominant systems, which refer to the dominant phase of the heat-transer fluid (water in all cases I'm aware), that is, liquid or steam. I'm not aware of any gas-based heat transfer, though you might want to add CO2 to your list as a potential working fluid. The phase-transition of steam from hot to cold side achieves much of the delivered power, and you'd be missing out on this with a purely gaseous medium. There are also both naturally occurring and enhanced sites. The former employ some existing geothermal site on Earth's surface, typically geysers or volcano. The latter can be sited anywhere, using a borehole. The difference being that drilling is far more expensive than tapping into an existing near-surface structure. The system Homer-Dixon is describing is a very deep borehole --- tens of kilometers rather than a few thousand meters. Geothermal heating utilises the direct thermal potential of the ground, rather than generating electricity (or as an adjunct to having generated electricity). These concepts range from existing / opportunistic siting such as hot springs or hot baths, to technically-coupled heat transfer and/or storage through heat pumps with a ground-loop component. There are also passive designs which simply utilise the insulating capabilities of soil or bedrock. Thick-walled adobe or stone structures thermoregulate by sheer thermal mass (possibly with other elements to increase or reduce solar gain and airflow). Sub-grade, semi-underground, or backfilled structures operate similarly. Seasonal thermal energy storage may be incorporated into single structures or at a community level in which excess summer heat is transferred to a thermally-stable geographic strata, and recovered from the same in winter. This requires that the subterranian layer not have a substantial heat flow, e.g., groundwater which would convey stored heat or cold away. There are also structures which exhibit an unwanted thermal effect over time. Many deep mines are hot and require active cooling of airflows. The London Underground subway system runs through rock strata which have absorbed heat from equipment and passengers for over a century, and whilst initially cool, is now unpleasantly warm. Plans to actively cool not only the void space (air) but the surrounding rock are now being explored.

ncmncm 4y ago

They quoted $50,000 to $90,000 for me. That would be quite some years' bills. Near-surface geothermal seems a better investment, if you have room for it.

wkearney99 4y ago
State and federal tax credits offset it somewhat. There's also the benefit of, y'know, not burning fuels at the site. My paying somewhat more over time for the initial outlay seems a reasonable expense. A purely selfish side-effect is NO NOISE from outdoor condenser fans. Three of them necessary would have wasted a lot of space too, and been more maintenance items. Near surface only works if you've got a lot of square footage to spread it out. The average suburban lot would not have the space for it (I thought that would have been obvious).
- ncmncm 4y ago
  As I said, "if you have room for it".

benj111 4y ago

You're talking about a ground source heat pump though? Which is distinct from geothermal.

ncmncm 4y ago
The sales people all call it geothermal. We might need to retroname the old one... Geosteam? Borehole? Maybe a closed-cycle nitrogen or helium turbine would make for fewer overhauls, thus lower maintenance cost, vs. exposing your turbines to superheated steam all the live-long day.
- dredmorbius 4y ago
  The two broadest classifications I see are Geothermal Power Generation and Geothermal Heating. These each have further subdivisions (and may be combined, as in a generation-heating facility, fairly common in Iceland). Generation can be divided in several ways. There are vapour and fluid-dominant systems, which refer to the dominant phase of the heat-transer fluid (water in all cases I'm aware), that is, liquid or steam. I'm not aware of any gas-based heat transfer, though you might want to add CO2 to your list as a potential working fluid. The phase-transition of steam from hot to cold side achieves much of the delivered power, and you'd be missing out on this with a purely gaseous medium. There are also both naturally occurring and enhanced sites. The former employ some existing geothermal site on Earth's surface, typically geysers or volcano. The latter can be sited anywhere, using a borehole. The difference being that drilling is far more expensive than tapping into an existing near-surface structure. The system Homer-Dixon is describing is a very deep borehole --- tens of kilometers rather than a few thousand meters. Geothermal heating utilises the direct thermal potential of the ground, rather than generating electricity (or as an adjunct to having generated electricity). These concepts range from existing / opportunistic siting such as hot springs or hot baths, to technically-coupled heat transfer and/or storage through heat pumps with a ground-loop component. There are also passive designs which simply utilise the insulating capabilities of soil or bedrock. Thick-walled adobe or stone structures thermoregulate by sheer thermal mass (possibly with other elements to increase or reduce solar gain and airflow). Sub-grade, semi-underground, or backfilled structures operate similarly. Seasonal thermal energy storage may be incorporated into single structures or at a community level in which excess summer heat is transferred to a thermally-stable geographic strata, and recovered from the same in winter. This requires that the subterranian layer not have a substantial heat flow, e.g., groundwater which would convey stored heat or cold away. There are also structures which exhibit an unwanted thermal effect over time. Many deep mines are hot and require active cooling of airflows. The London Underground subway system runs through rock strata which have absorbed heat from equipment and passengers for over a century, and whilst initially cool, is now unpleasantly warm. Plans to actively cool not only the void space (air) but the surrounding rock are now being explored.